This invention relates to an advance mechanism for a mine roof support assembly.
A known type of mine roof support assembly is constituted by a plurality of roof support units positioned side-by-side along, for example, a longwall face. Each of the units has a roof shield supported on a floor sill by means of hydraulic props. The floor sill may be constituted by a pair of spaced-apart floor girders. In order to advance the assembly to follow the advance of the longwall face, the roof support units are advanced, individually or in groups, by means of hydraulic advance rams. During the advance of any given unit, its hydraulic props are relaxed so that its roof shield is not under load.
A known type of advance mechanism for such an assembly comprises a pair of resilient guide rods and a hydraulic advance ram. Such an advance mechanism can be positioned between the floors sills of each pair of adjacent roof support units. Alternatively, where a pair of floor girders constitute each floor sill, a respective advance mechanism can be positioned between the two floor girders of each roof support unit. In either case, the front ends of the guide rods of such an advance mechanism are attached, for example, to a longwall conveyor, and the rear ends are coupled together by means of a cross-piece. The advance ram acts on the cross-piece, the floor sill or sills providing an abutment for the ram. The cross-piece is longitudinally displaceable in slideways provides in the mutually facing sides of the two girders constituting one floor sill, or in the mutually facing sides of two adjacent floor sills. (Typical prior art arrangements are disclosed in DT-OS Nos. 2527054, DT-OS 2522111, DT-OS 25223094, DT-Gbm 1993011, DT-OS 2540091 and DT-OS 2547853).
The aim of the invention is to provide an advance mechanism for a mine roof support assembly which is simple and robust, and which serves to guide and orientate the associated roof support unit in a reliable manner even where the face is steeply inclined.